RATIONALE: Drugs used in chemotherapy, such as paclitaxel, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Lapatinib may help paclitaxel work better by making tumor cells more sensitive to the drug. Lapatinib may also stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Giving lapatinib together with paclitaxel may kill more tumor cells.